Methane production of raw and composted solid waste in simulated landfill cells

Abstract

Methane contributes approximately 20% to the annual increase in global warming, and is explosive at concentrations of 5 to 15% in air. Landfills are the origin of approximately 15% of the total global methane emissions. This study was conducted to determine the potential decrease in methane production from municipal landfills if the organic compo nents of solid waste (SW) are composted prior to landfilling. The quantities and rates of methane production were mea sured using simulated landfill cells containing composted and raw simulated SW. The SW was composted in an open pile and characterized by temperature, pH, ash content and CO₂ evolved during aerobic respiration. Assuming a 10% lignin content, the labile carbon fraction was reduced by an esti mated 71% during composting. Over a 6-month period, sim ulated landfill cells filled with raw waste generated 66 liters methane per kg of dry refuse, while cells containing com posted SW produced 31 liters methane per kg of dry compost. Per unit weight of the original dry raw SW, composted SW placed in a simulated landfill environment produced only 15 liters methane per kg dry raw SW which is 23% of the meth ane that was generated when the raw SW was placed directly in the simulated landfill cells.